Bus Overview; Modifying The Impedance Of The Various C-Bus Cables - Siemens FC700A System Planning Manual

6.1

Bus overview

Features C-Bus
Field of applica-
tion
Local system bus
Speed of trans-
57kBaud
mission
Length of line
Max. 1000m
(G51 ∅ 0,8: 1400m)
Number of users
... 16
connected or
C-Bus devices
addresses
Number of wires
(+3 wires for emer-
gency operation)
Type of cable
Twisted 1)
Loop line
T-branch
Short-circuit proof
Each user con-
nected with line
separator
Network structure Master/master
Scanning
Event-controlled,
presence monitoring
Principle
Serial Bus
- Cerberus protocol
- Collision detection
- Manchester coding
6.2

Modifying the impedance of the various C-Bus cables

Siemens Building Technologies
Fire & Security Products
I-Bus
Inside control unit
1000kBaud
Max. 3m (only
inside cabinet)
... 16
I-Bus modules
2
26
Flat cable
–
– –
Yes
–
Master/slave
Cyclic,
Event controlled
C-Bus
- Cerberus protocol
- SPI/Motorola
1 Calibrated according to cable impedance: 50Ω (MICC) / 110Ω (G51, ø
0.8mm, not shielded)
C-Bus standard cables have a characteristic impedance of 110Ω. The driver and
end-of-line resistors are soldered to solder lugs and can be adapted accordingly
with other characteristic impedances (see diagram chapter 6.2.1).
1. Explanation
A cable must be terminated with resistors. The resistance value must correspond
to the impedance of the cable. Each C-Bus user has four end-of-line resistors
(Ri). In addition two driver resistors (Rd) are integrated on the p.c.b. In order that
the resistors can be exchanged easily they are all soldered to solder lugs.
C-Bus p.c.b.
B3Q700
E3H020
The driver resistors specify the current on the C-Bus. In order that the signal on the
C-Bus always has the same amplitude (1.35Vpp), the following correlation is valid:
Rd = Ri x 3,65
SynoLOOP SynoLINE600
For addressable For collective
detectors detectors
(Direct current
2 messages/sec
Max. 150Ω/300nF
150/250Ω/4µF
See chapter 16
See chapter 16
1 address
... 128
(Max. 25 detec-
D-Bus devices
2
Twisted Twisted
(Un-twisted per- (Un-twisted
missible) permissible)
–
Yes
Each user con-
nected with line
separator
Master/slave Master/slave
Cyclic
- typ. all 64s
- Interrupt on
alarm
Sensor/actor-Bus
- Cerberus proto- Conventional
col 'K31' - Current gain
- Serial 8bit principle
- Start-up: daisy- - Voltage levels
chain
Ri
R31 ... R34
R173, R174, R177, R178
(45Ω < Ri < 200Ω)
LON-Bus
Local data bus
for floor indicator
panels
78kBaud
signal)
Max. 500m as
Max.
free topology
Max. 1000m as
stub line
... 32
LON-Bus de-
tors) vices
2 2
Twisted
– –
–
(See chapter 18)
No No
Master/slave
Event-controlled,
presence moni-
–
toring
(All 60s)
Network
- Echelon Chip
(LON protocol)
- Cerberus
specific telegram
Rd
R49, R50
R180, R183
Bus systems
Data Bus
Local data bus
parallel ind.
panel, synoptic
panel or relay
SPI-Bus 2KHz
Max. 1000m
... 24
Max. 8 addresses
6
(+3 wires supply)
Twisted
–
–
Yes
Master/slave
Cyclic
- typ. all 250ms
Serial bus
- Cerberus proto-
col
15
007836_a_en_--.doc
03.2004